Apple fruit periderms (russeting) induced by wounding or by moisture have the same histologies, chemistries and gene expressions

Abstract

Russeting is a cosmetic defect of some fruit skins. Russeting (botanically: induction of periderm formation) can result from various environmental factors including wounding and surface moisture. The objective was to compare periderms resulting from wounding with those from exposure to moisture in developing apple fruit. Wounding or moisture exposure both resulted in cuticular microcracking. Cross-sections revealed suberized hypodermal cell walls by 4 d, and the start of periderm formation by 8 d after wounding or moisture treatment. The expression of selected target genes was similar in wound and moisture induced periderms. Transcription factors involved in the regulation of suberin (MYB93) and lignin (MYB42) synthesis, genes involved in the synthesis (CYP86B1) and the transport (ABCG20) of suberin monomers and two uncharacterized transcription factors (NAC038 and NAC058) were all upregulated in induced periderm samples. Genes involved in cutin (GPAT6, SHN3) and wax synthesis (KCS10, WSD1, CER6) and transport of cutin monomers and wax components (ABCG11) were all downregulated. Levels of typical suberin monomers (ω-hydroxy-C20, -C22 and -C24 acids) and total suberin were high in the periderms, but low in the cuticle. Periderms were induced only when wounding occurred during early fruit development (32 and 66 days after full bloom (DAFB)) but not later (93 DAFB). Wound and moisture induced periderms are very similar morphologically, histologically, compositionally and molecularly.

Microscopic and metabolic investigations disclose the factors that lead to skin cracking in chili-type pepper fruit varieties

“…Lastly, we stained skin tissues with the fluorescent Fluorol Yellow 088 (FY 088) dye previously shown to interact with hydroxycinnamic components in the fruit skin cuticle, in addition to the suberized periderm cells in case formed in fleshy fruit such as reticulated melon [ 13 ], apple [ 53 , 54 ], mango [ 55 ], and cucumber [ 11 , 14 ]. Herein, the non-cracked skin of Numex Garnet displayed an intact cuticle throughout fruit development as detected both in Sudan IV ( Fig.…”

Time course of changes in the transcriptome during russet induction in apple fruit

“…Earlier studies established that (1) microcracking of the cuticle occurs within 48 h of moisture exposure and (2) periderm initiation begins within 24 h of moisture removal [ 13 , 14 , 21 , 43 ]. Therefore, putative regulators must be expressed early during Phase I and at the beginning of Phase II, i.e., at ‘12 d wet + 1 d dry’.…”

“…The expression patterns of the selected genes were similar for RNA-Seq and qPCR. MYB93 was used to trace the early processes of suberin synthesis [ 21 , 27 , 43 ] during Phase II and thus was representative of periderm formation as indexed by the occurrence of phellem cells.…”

“…Mechanical wounding of apple fruit skins induced russeting. Hence, the expression patterns of the DEGs were also analyzed following wounding [ 43 ].…”

“…These arguments demonstrate that moisture-induced russeting offers a high degree of control. The system was successfully used previously [ 13 , 14 , 21 , 43 ]. The data obtained demonstrate that during Phase I within 48 h of moisture exposure, cuticle synthesis decreases, and microcracks are formed.…”